The anti-platelet drug abciximab, delivered directly to lesions caused by a heart attack, significantly decreased damage to the heart muscle in high-risk patients while clot aspiration showed no impact, according to research presented today at the American College of Cardiology's 61st Annual Scientific Session. The Scientific Session, the premier cardiovascular medical meeting, brings cardiovascular professionals together to further advances in the field.
Angioplasty is performed during a heart attack to restore blood flow and reduce the size of the infarct - permanent damage to the heart muscle - which begins within minutes after the onset of chest pain and can continue for up to 12 hours. Too often, however, heart damage is extensive. In some cases the culprits are distal emboli, plaque or blot clots that break off during angioplasty and lodge in smaller vessels, essentially moving the heart attack downstream to smaller arteries.
Two approaches to prevent this process have been studied extensively with highly conflicting results: (1) delivering high concentrations of abciximab to the blood clot (thrombus) at the site of the lesion, where it keeps platelets from sticking together and causes the clot to collapse, and (2) sucking out the clot through a process called manual aspiration thrombectomy.
"All of the earlier studies have limitations," said Gregg W. Stone, MD, director of cardiovascular research and education, Columbia University Medical Center/New York-Presbyterian Hospital, New York City, and principal investigator of the INFUSE-AMI trial. "To clarify which approach, if any, can reduce the size of the heart attack, we studied only patients presenting within four hours of symptom onset with a large anterior heart attack, with blockage of the largest heart artery confirmed by cath lab. These are destined to be very large heart attacks, but the patients presented early enough for us to be able to reduce the amount of damage."
INFUSE-AMI used a 2 x 2 factorial design, which isolates the impact of each intervention to maximize the chance of identifying any reduction in heart attack size. The trial, conducted at 37 sites in six countries, screened 6,318 patients and enrolled 452 (7.2 percent). It is a single-blind study in which the operator knew the randomization assignments.
Participants were randomly assigned to one of four arms: (1) aspiration plus abciximab; (2) aspiration without abciximab; (3) no aspiration plus abciximab; and (4) no aspiration or abciximab (control). In the two abciximab arms, a "weeping" balloon catheter delivered the drug right to the site of the lesion, which "invariably has a thrombus," Dr. Stone noted. A catheter was used to aspirate clots. All patients who had angioplasty were given bivalirudin, an anticoagulant that keeps bleeding and mortality low.